Research projects and systems products soon will have bandwidth, responsiveness, and/or real-time requirements that exceed the capabilities of existing LANs. For example, the ongoing transition from paper to electronic formats for documents ranging from personal papers to technical libraries is leading to the development of advanced electronic scanning and printing devices, which have bandwidth requirements that will continue to increase, not only as the speed and resolution of these devices increase, but as the color and gray scale capabilities of these devices are extended. Another example of the demand for improved LANs centers on the high-quality video imagery that is envisioned by some of the emerging collaborative technologies, such as the Xerox Media Space, which utilize live video links and meeting-support systems that are based upon wall-sized display systems. Furthermore, high performance computers are becoming affordable for use as computing resources, high-performance file servers, visualization workstations, etc., but the LANs that are now in use do not have the capacity that is needed to support these higher performance computers.
The more demanding of the potential scientific computing and visualization applications require gigabit-per-second (Gbps) data transfer rates, but bandwidths in the 10-100 Mbps range are sufficient for the majority of the perceived applications. However, some of these applications, such as real-time video, will place a more continuous load on the network and require one-to-many ("multicasting") transmission in addition to point-point ("unicast") links. Therefore, a reasonable working assumption is that LANs soon will require aggregate bandwidths in the 10-40 Gbps range for supporting a more or less ordinary community of users simultaneously. Different user communities typically have different needs, and the requirements of any given user community generally expand over time, so there is a need for a high performance LAN that scales gracefully and economically to satisfy the requirements of its user community.
Known FDDI (Fiber Distributed Data Interface) networks fail to meet either the peak or aggregate bandwidth requirements of the LAN that this invention envisions. Furthermore, many of the other recently developed technologies, such as those that are based upon crossbar switches or high-speed broadcast busses, appear to fall short of satisfying the multicast, broadcast and/or affordability requirements of the proposed LAN.